PLATE XXVII 



PAGE 



Figs. 1-5. EOOBTHIS DESMOPLEURA (Meek) 237 



1. Brachial valve enlarged. 



2. Pedicle valve, with characteristic surface. 



3. 4. Cast of pedicle valve and side outline of same. 



5. Exterior of pedicle valve showing surface characters. 



Ordovician (Ozarkian ?), El Paso County, Colorado. 



Figs. 6-8. SAUKIA STOSEI Walcott 351 



6. Surface of limestone with cranidia, free cheek, and pygidium 



weathered out in relief. X 3. 



7. Side view of cranidium and free cheek shown in Fig. 6. X 3. 



8. Another view of cranidium and free cheek shown in Fig. 6. 



Cambrian (Ozarkian), Conococheague Is., near Scotland, 

 Franklin County, Pennsylvania. 



Fig. 9. FOSSIL BEEF-FORMING CALCAREOUS ALGAE 190 



Photograph of a rock mass forming the edge of a reef of fossil algae 

 (Cryptozoon) overlapped by stratified layers of the argillaceous 

 Conococheague limestone. This algal growth developed regular 

 concentric layers in its lower part (A), but these layers or 

 laminae became rather loosely interwoven in the upper portion 

 (B). In the upper righthand corner (C) the overlapping edges 

 of laminated Conococheague limestone may be noted. One- 

 eighth natural size. 



Cambrian (Ozarkian), Conococheague Is., one mile south of 

 Clear Spring, Maryland. 

 Figures 1 to 8 are after Walcott. 



377 



